Speedometer.



G. W. BLACKBURRL SPEEDO APPLICATION FILED MAR. 19, la

METER.

Patented Dec. 31, 1918.

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APPLICATION FILED MAR-19, Hi7. L g yifio Patented Dec. 31, 1918.

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SPEEDOMETER.

APPLICATlON FILED MAR. 19. war.

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Patented Dec. 31, 1918.

G. W. BLACKBURN.

SPEEDOMETER.

APPLICATION FILED MAR. 19. 1911.

Patented Dec. 31, 1918.

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ii in GUY W. BLACKBURN, OF ELGIH, ILLINOIS.

SPEEDOMETEB.

Specification of Letters Patent.

Application filed March 19, 1917. Serial No. 155,702.

To all whom it may concern:

Be it known that I, GUY W. BLACKBURN, a citizen of the United States,residing at Elgin, in the county of Kane and State of Illinois, haveinvented a certain new and useful Improvement in vSpeedometers, of whichthe following is a specification.

My invention relates to improvements in speedometers and has for oneobject to provide a new and improved form of speedometer, which willindicate the speed of a moving vehicle. It isunderstood, of course, thatthe speedometer features might equally well be adapted to otherpurposes, that is to say, this speedometer, by changing the scale, willoperate as a tachometer or revolution counter, or instrument forregistering the speed or velocity of a moving shaft, a moving vessel orvehicle as the case may be, and while I have referred to it as aspeedometer and illustrated a form which would be particularly adaptable1n connection with an automobile as a speedometer, it is obvious thatthe invention is not so limited. One object of the invention is toprovide a speedometer which will be peculiarly sensitive and accurate.'Another object is to provide a speedometer wherein the connectionbetween the indicating and re cording mechanism and the moving part is aflexible and adjustable connection. Another object is to provide anelectric connection between the moving shaft and the indicatingmechanism. Other objects will appear from time to time in thespecification.

The invention is illustrated more or less diagrammatically in theaccompanying drawings, wherein v Figure 1 is a front elevation on scale;

Fig. 2 is a plan view of the mechanism with the casing in section;

Fig. 3 is a section along the line 3-3 of Fig. 2;

Fig. 4 is a section Fig. 2;

Fig. 5 is a section along the line Fig. 2;

Fig. 6 is a section along the line 6-6 of Fig. 2;

Fig. 7 is a rear elevation of the parts shown in Fig. 6 looking in thedirection of the arrow 7 in Fig. 6;

Fig. 8 is a detail of the dash-pot shown in Fig. 6 showing the leakport;

a small along the line 4-4 of Fig. 9 is a wiring diagram showing partsin elevation with parts omitted and parts in section;

Fig. 10 is a plan view of part of the mechanism shown in Fig. 9;

Fig. 11 is a section on the line 1111 of Fig. 10.

Like parts are indicated by like figures in all the drawings.

A. is a housing or casing provided with a transparent window A and anopaque back A which is perforated as indicated to permit the operator tosee a portion of the indicator wheel A*. This indicator wheel has markedon it about its periphery numerals or characters to indicate miles perhour, a central line is inscribed across the transparent window in thecenter of the perforation to mark and make easy the reading of thewheel. A is a trip record, and A a season mileage record on a mileagecounter, WhlCh I have not otherwise specifically shown, but which ofcourse forms an integral part of any automobile speedometer. A is thedrive shaft adapted to operate the mileage counter by means of a wormwheel A driven from a worm shaft A This worm shaft A is rotatablymounted in a bearing A on a bracket A and carries at its inmost end amiter gear A. A is a pinion rigidly attached to the wheel A in mesh witha rack A This radk is slidably mounted in guides A, and is adapted torotate the wheel.

B is a ring frame or armature mounted on the base or bottom B of thehousing A.

Patented Dec. 31, 1918.

Equally spaced about its periphery are three magnets B B", B. Thesearmatures haveprojecting forwardly therefrom and away from the magnet,connecting rods B and these connecting rods are pivoted to a star hubB", which hub in turn is pivoted on a crank pin B eccentrically mountedon the end of the shaft B". This shaft B is 1'0- tatably mounted in abearing B on the bracket A, and in a bearing B on a bracket B, and arotation of the crank pin about its center causes a rotation of theshaft B. B is a miter gear keyed to the shaft B in mesh with the miterpinion A", so that a rotation of the shaft B will result in a rotationof the shaft connecting and operating the mileage recorder.- B" is ashort screw-threaded member slidably mounted on the shaft B, and splinedof movement of-the vehicle or the speed of rotation of the shaft, thecharacteristics of which are to be recorded or indicated. I

will now describe the operating connection.

between this motor and the vehicle wheel.

G is a rotating part of the vehicle wheel or shaft. It carries a cam C.C is a slidable pin provided at one end with a cam roller C inopposition to the cam C. A spring C is adapted to hold this cam rollerin the path of the cam and return it to the position shown in Fig. 1after each move.-

ment by the cam.' C is a foot pivoted on the free end of the shaft orpin C? and limited so far as its counter clockwise movement with respectto that shaft is concerned, by a pin C while it is free to move in theopposite direction. C is a rotatably mounted cam Wheel having camfingers C, C", C.

These fingers project into the path of the member C and it is obviousthat at each rotation of the wheel when the pin C is moved away. fromthe wheel, the member C will catch one of the fingers C C, C and move ita third of a revolution. The

sprin ber C moving a little to one side on pivot connection,if'necessary, and the parts will' be ready for the next step. Upon theface of the cam wheel C are a series of three separate contact segments,C C and C These segments are each insulated one from another by thewheel itself which is preferably made of insulating or nonconduct-- ingmaterial. They are, however, electrically connected to the central hubfrom which a conducting wire C leads to a battery or other suitablesource of electric power 0 From this battery a conductor C leads to eachof the electro-magnets B B 13*. C" is a conductor leading from theelectro-magnet B to a spring contact finger C in opposition to thecontact segment C C is a conductor leading from the electro-magnet B tothe spring contact finger C in opposition to the contact segment C. C isa conductor leading from the electromagnet B to the spring contactfinger C in opposition to the contact segment C 4 It will be evident, ofcourse, that as the wheel C rotates at each rotation thereofthe part Cwill engage one of the fingers C, C and rotate the switch hub through athird of a revolution, so that the switch hub makes one full revolutionfor each three revolutions of the wheel. This mechanism is will thenretract the pin, the mem-j meat-are all mounted downon the running gearimmediately adjacent the wheel, and the only connection between it andthe speedometer is in the electric conductor above described.

With the parts in the position shown in Fig. 9, the electro-ma et B willbe energized, the armature will be pulled down by such magnet so thatthe parts are in the position shown in Fig. 3. At the next reciprocationof the sliding rod the finger C Wlll come in contact with the segment Cand the magnet B will be energized pulling the armature upward androtating the shaft B through a third of a revolution in a clockwisedirection. -The next rotation of the wheel will bring the contactsegment G" into engagement w1th the finger C to energize the magnet B,thus pulling on the armature and rotating the crank shaft toanotherthird of a revolution. The next movement the parts will return tothe position shown in'Figs. 9 and 3. Thus, as the vehicle wheel rotatesthe shaft B will be rotated at a speed directly proportional to therotation or speed of the vehicle by a series of separate increments, andthis rotation will continue just as long as the rotation of the vehiclewheel continues and so long as the current is provided by the storagebattery or the source of power there will be a direct relation betweenthe vehicle speed and the rotation of the "main shaft B. This takes careof the odometer or distance counter because its reading depends onlyupon the number of revolutions of the vehicle wheel and will not beinterfered with by the speed indicating mechanism subsequently to bedescribed.

The wheel D is mounted on a part directly and positively driven by therotation of the vehicle Wheel. This wheel is provided with a series ofoutwardly projecting paddles or vanes D spaced in the preferred formabout a third of the circumference apart though they might bedifferently positioned with respect to the wheel. D is a trough in whichthe vanes D travel. The trough extends up on both sides of the wheel andmakes a snug fit all the way around with the sides ofthe wheel and thesides and outer surfacesof the paddle. Inthis trough is a small amountof mercury D. This mercury is adapted to be carried up as the shaftrotates and discharged by the paddle into the cup D from which it runsback gradually through the passage D minal finger extending downwardlyinto the cup D adapted when the cup is filled by the rotating paddle tomake the contact with the mercury and close the circuit. The size of thepackage and the amount of mercury lifted up by each paddle is such thatthere is always mercury in the cup whenever the vehicle is moving, butif the vehicle should stop moving, there would be no mercury added tothe cup to take the place of that the frame E carrying a yoke E whichleaks out through the little passage, andso the contact would be broken.

E E aretrack bars parallel with the shaft B held in position by suitablebrackets E as indicated. E is a roller carriage adapted to travel; alongthe track E. This carriage has downwardly extending therefrom which yokerests upon the shaft B and engages the two ends of the worm B which wormis splined on and free to slide along but held against,

rotation about the shaft 13. Projecting outwardly from the yoke E is anarm E" and this arm is pivoted on the rack A so that as the carriage Emoves back and forth along its track the rack moves with it. E is a dashpot cylinder. It is suspended on the rod E by arms E one of which isengaged by a finger E on the carriage E so that carriage and dash potmove back and forth together along the track E. This dash pot contains apiston E slidable therein and inside of the dash pot interposed betweenthe closed upper end thereof and the piston is. a spring E". E is anexhaust passage passing through the closed end. of the dash pot adaptedto be controlled by the valve E so that the passage of air into and outof the dash pot cylinder proper may be nicely regulated by the operator.

The piston E is provided with a downwardly extending piston rod F. Thisrod is pivoted to a linklike member F which member has pivoted at itsother end a sharp contact roller F F is a frame attached to the centerof the linklike lever and supporting its frame being pivotally andslidably mounted on the track E F is an elongated tapered fluted cammember having three vanes adapted to be engaged by the contact wheel FThis cam member is rigidly mounted on the shaft F which shaft isrotatably mounted at one end in the bracket A as indicated and at theother end in a bracket B and has on its end a gear F in mesh with a gearF on a shaft F which shaft carries a screw F in mesh with and parallelwith the worm B Mounted on the shaft F between the end of the cam memberF and the pinion oh the end of the shaft are three circuit making andbreaking cam members G, G, and G These members each extend aboutone-third of a revolution and have opposed to them spring contactfingers G G and G respectively which fingers are mounted upon aninsulating block G so that they are insulated from the armature of theapparatus while the cam member is not.

It will be noted in this connection that the tracks E E are alsoinsulated from the armature of the mechanism in that the bracketssupporting them are mounted upon insulating blocks and in that the yokeE is made of insulating material. Leading from the contact fingers G",G, Gr are cOnductors G, G and G the conductor Gr leading to anelectro-magnet G", the conductor G leading to an electro-magnet G? andthe conductor G leading to an electro-magnet G These electro-magnets areeach of them provided with. armatures G G G which armatures haveconnecting-rods G extending to a star wheel G16 pivoted on a crank pin Gas shown on the end of the shaft.

H is' a brake drum on the shaft F". H

is a brake leaf pressed yieldingly against the brake drum H by thespring H. H is an armature carried by. the member H in opposition to anelectro-magnet H Conductors H H and H lead from the electromagnets G G,G to the electro-magnets H and a conductor H leads from theelectro-magnet H to a suitable source of electric power, for instance, abattery H The conductor H leads thence to the base plate H whereby itisin electric connection with the track member E It will be evident thatwhile I have shown in my drawings an operative device still many changesmight be made both in size, shape and arrangement of parts withoutdeparting materially from the spirit of my invention and I wishtherefore that my drawings be regarded as in a sense diagrammatic.

The use and operation of my invention are as follows:

When the vehicle is at rest the driving electric circuit is dead becausethe mercury will have run out of the conducting or controlling cup-tobreak the circuit. As soon as the vehicle commences to move, mercurywill be fed to the contact cup on the vehicle axle with the firstmovement of the wheel. This completes the circuit and then as the wheelturns each movement of the cam member past the push rod will drive thecontroller wheel on the axle through one-third of a revolution thuscausing the electro-magnetic engine to operate because as eachelectromagnet is successively energized it will pull its armature in torotate the crank shaft through one-third of a revolution and the fasterthe vehicle wheel turns the more frequently will the different armaturesbe energized and the more rapidly will the splined shaft rotate and thusthe splined shaft will rotate at a speed directly proportional to therotational speed of the vehicle shaft carrying with it the worm and alsodriving the odometer or distance indicator.

The rotation of the splined shaft in consonance with the rotation of thevehicle shaft then operates the odometer and gets a direct and positivereading if properly calibrated for the distance covered by the vehicle.

As the splined shaft rotates with the vehicle and as the worm carried byit rotates,

that worm, which will then be in mesh with the long screw, will travelas shown in Fig. 9 toward the left, thus moving the carriage and all itsassociated parts with it toward the left. The result of this will be tobring the contact roller into engagement with the three-branched flutedcam and complete or close the circuit through the controlling system.The controlling electromagnet will then commence its rotation and rotateboth the long screw and the cam, and this rotation of the long screwwill be opposed in its effect to the rotation of the splined shaft andwill tend to cause the worm to move back toward the zero position.-

Each time that one of the cam members lifts up the contact roller anddrops it, the spring in the dash pot will push it down to complete thecircuit at the base of the next cam leaf and during the time occupied bythe fallof the roller the circuit will be broken, no current will passand the controlling system will be at rest. As soon as contact is made,rotation starts until the contact roller is again thrown off.

The nearer the carriage is to the zero position the farther must thecontact roller drop and the longer will it take, and since the wormrotates all the time the carriage will be moved toward the left duringsuch dead period in the controlling system. Thus a condition ofequilibrium will soon be reached at which the distance moved by the wormduring the dead period is equal to. the distance gained by the thread inmoving the worm back during the energized period of the controllingsystem and the faster the vehicle travels the farther toward the leftwill this place be, because if the vehicle travels fast the dead periodmust be short to enable the screw to bring the worm back and the deadperiod is shorter when the carriage moves up toward the left where thefall of the contact roller is short.

The time of fall may be adjusted by the operator by changing the size ofthe opening through which the air rushes in to the dash pot, and thisadjustment is used for properly calibrating the instrument. It theopening is wide, the spring will throw the contact roller down rapidly.If the opening is small, the time for the fall of the contact rollerwill be increased.

'The circuit breaker operates to break the vehicle controlled circuitwhen the vehicle comes to'a rest but the timing circuit is not brokenuntil the speed indicator is returned to the zero position as indicated.

When the vehicle comes to rest, the driving system stops, but thecontrolling system continues. the screw rotating by short spells ofactivity and quiet until the worm has been propelled down to the extremeright when the contact roller finally gets clear oif the cam, thusbreaking the circuit aeaeao and stopping operations until the circuit isagain closed by the operation of the driving system.

It will be understood that by means of the two electro-magnetic motorswhose speed can be positively controlled so that they only run whenpower is on and stop control the whole system to give a direct andabsolute velocity reading. It will be understood also that if there isoverrunning of one system or the other after the power is off, it willbe balanced by a substantially equal tendency toward overrunning in theother system and thus no inaccuracy can possibly develop when the deviceis properly adjusted and properly calibrated.

As soon as the timing circuit is closed, the electromagnetic motordriving the timing or electric mechanism commences to operate, becauseone of the electromagnets is always in the operating position and bypulling on its armature will rotate the shaft.

This shaft as it rotates drives the cam shaft and the rotation of thecam shaft operates by means of the conducting fingers and the circuitmaking and breaking cam members to cause successive electromagnets to beenergized thus continuing the rotation of the shaft.

It will be noted that the spring held brake is draWn away fromengagement with the brake drum by its electromagnet which is in circuitwith each of the electromagnets forming the engine so that whenever thedevice is in operation the brake is off but whenever the circuit is openthe brake automatically goes on.

If there were a permanent connection between the source of power and thecircuit making and breaking cams the speed at which the timing enginerotates would be limited only by the electric power available and thefrictional resistance of the load carried and no-speedometer readingcould be obtained. In order to get the speedometer or speed reading,therefore, directly proportional to and responsive to the speed at whichthe vehicle is traveling, I have provided an automatic control means forcontrolling the operation of the timing engine which has previously beendescribed.

This automatic control operates by cutting off the current .in thetiming engine for variable short time intervals depending on the speedof the vehicle and thus controlling the speed of the timing engine.

If the screw driven by the timing engine were at rest the worm driven bythe other meaaao engine would climb u the screw tending to move towardthe lei t in Fig. 9. If the timing engine ran at full speed withoutcontrol the screw would run away from the worm and the ,worm would tendto move toward the right in Fig. 9.

My controlling mechanism, therefore, provides means for controlling thespeed of rotation of the screw so that the tendency of the worm totravel in one direction and of the screw to draw it in another iscounterbalanced or equalized until the worm comes to rest so far as itslongitudinal movement along the splined shaft is concerned at a pointdirectly proportional as the instrument is calibrated to the speed ofthe vehicle.

It ill be understood that it takes three revolutions of the vehiclewheel to make one revolution of the electro-magnetic driving enginebecause the three electromagnets in the engine must each make one stroketo make a full revolution of the engine shaft and by the cam arrangementdriven by the vehicle wheel this can only be possible when threestrokes, that is to say, three revolutions of the vehicle wheel, havebeen made. It is obvious, of course, that if the rotational speed of thevehicle wheel is sufiiciently slight, there will be a pause between eachone third revolution of the electromagnetic engine, because the instantthe circuit is closed the engine will rotate a third of a revolution,and then stop, though conceivably of course at very high speeds theengine may not have time to complete its revolution much, if any, beforethe inv creased impulse is given.

It will be understood that the controlling engine travels also by aseries of successive stops, there being a pause between each stop so asto give the contact wheel time to drop from the crest of one cam leaf tothe base of the next. Thus these two engines operate by stops withpauses between. The device is arranged so that as these two enginesdrive the indicator in opposite directions, there comes a time when, asthe indicator moves along and as the contact roller moves along the cam,the stops coincide so that finally you reach a point after the carriagehas completed its upward movement where the pauses in the two systemsoccur at the same time, and the driving impulse in the two systems occurat the same time, thus there is no movement of the indicator orcarriage. If the speed changes there will be a gradual step by stepmovement until the indicator assumes a new position, where the timebetween the impulse given by the vehicle wheel equals the time betweenthe impulse controlled by the drop of the conductor roller, and thisrelation will prevail with all speeds of the vehicle, because while thetime between impulse by the roller wheel partially driven by said motor,and means for'driving said indicator in opposition to said motor, thespeed at which such opposition driving means are'operated beingcontrolled by the-position of the indicator.

2. A speedometer for motor vehicles and the like comprising anindicating mechanism, two separate driving means therefor adaptedconjointly to operate upon the indicating mechanism to drive it indifferent directions at different speeds, the speed of one of saiddriving mechanisms varying independently of the indicating mechanism,the speed of the other being directly dependent upon and controlled bythe indicating mechanism.

3. A speedometer comprising two meshing screw-threads pitched in thesame direction movable longitudinally with respect one to another, meansfor driving them separately and in the same direction, the driving speedof'one of said screws being independent of their relative longitudinalposition, the driving means for the other being adapted to change itsspeed in response to the change in longitudinal position of the twoscrews with respect one to another.

4. A speedometer comprising two meshing screw threads movablelongitudinally with respect one to another, means for driving themseparately, the driving speed of one of said screws being independent oftheir relative longitudinal position, the driving means for the otherbeing adapted to change its speed in response to the change inlongitudinal position of the two screws with respect one to another,said means comprising in both cases an electric motor the change speedmechanism being driven by said motor and comprising a cam adapted tomake and break the circuit driving said motor.

5. A speed indicator for vehicles and the like comprising a pair ofelectric motors, and means for driving said motors at all times when thevehicle is in operation, means for automatically discontinuing saiddrive upon the stopping of the vehicle.

6. A speed indicator for motor vehicles and the like comprising twodriving motors, an indicating motor, a driving connection between eachmotor and the indicator operating independently and in opposition.

8. A speed indicator for vehicles and the like comprising a pair ofelectric motors, means for driving them at controlled speeds, a movableindicator and driving connectlons between each motor and the indicatoroperating independently and "in opposltion, means for driving one ofsaid motors at a speed directly proportional to the vehicle speed.

9. A speed indicator for vehicles and the like comprising a pair ofelectric motors, means for driving them at controlled speeds,

- a movable indicator and driving connections between each motor and theindicator operating independently and in opposition, means for drivingone of said motors at a variable speed depending upon the position ofthe indicator.

10. A speed indicator for vehicles and the like comprising a pair ofelectric motors, means for driving them at controlled speeds, a movableindicator and driving connections between each motor and the indicatoroperating independently and in opposition, means for driving one of saidmotors at a variable speed depending upon the position of the indicatorand for driving the other at a variable speed directly responsive to thespeed of the vehicle.

11. A speed indicator for vehicles comprising a plurality ofelectro-magnetic motors, means for successively exciting the magnetsforming such motors to drive them, an indicator and driving connectionsbetween it and each motor operating separately upon it in opposition andmeans responsive to the position of such indicator for controlling thespeed at which one of said motors is driven.

12. A speed indicator for vehicles comprising a plurality ofelectro-magnetic motors, means for successively exciting the magnetsforming such motors to drive them, an indicator and driving connectionsbetween it and each motor operating separately upon it in opposition andmeans responsive to the position of such indicator for controlling thespeed at which one of said motors is driven such means comprising meansfor making and breaking the circuit a plurality of times during eachrevolution to successively excite the electro-magnets.

13. A speed indicator for vehicles comprising a plurality ofelectro-magnetic motors, means for successively exciting the magnetsforming such motors to drive them, an indicator and driving connectionsbetween it and each motor operating sepa- -rately upon it in oppositionand means responsive to the osition of such indicator for controlling te speed at which one of said motors is driven such means comprisingmeans for making and breaking the circuit a plurality of times duringeach revolution to successively excite the electro-magnets, said meanscomprisin a circuit making and breaking cam an a delay action circuitclosing means in opposition to said cam.

A speed indicator for vehicles 'comprislng a plurality ofelectro-magnetic molution to successively excite the electro-magnets,said means comprising a circuit making and breaking cam and a delayaction circuit closing means in opposition to said cam the said cambeing adapted .to control the length of time during which the circuit isopen between each excitation of the magnets.

15. A speed indicator for vehicles and the like comprisinga pair ofelectric motors and means for drlving such motors at all times when thevehicle is in operation, means operative immediately upon discontinuanceof the movement of the vehicle for automatically discontinuing theoperation of one of said motors and means subsequently operative forautomatically discontlnuing the operation of the other.

16. A speed indicator for vehicles and the like comprising a pair ofelectric motors and means for driving such motors at all times when thevehicle is in operation, means operative immediately upon discontinuanceof the movement of the vehicle for automatically discontinuing theoperation of one of said motors and means subsequently operative forautomatically discon-,

ating independently and upon the indicating mechanism, means for drivingone of said motors at a variable speed depending on the speed of thevehicle and means for driving the'other at a variable speed depending onthe position of the indicating mechanism.

18. A speedometer comprising two meshing screw threads pitched in thesame direction, one being longitudinally movable, the otherlongitudinally fixed, separate means for driving them, the driving meansof the movable screw being independent of the relative longitudinalposition of the screws and the driving means of the longitudinally fixedscrew being adapted to change its speed in response to the change inrelative longitudinal'position of the two screws.

19. A speedometer comprising two meshing screw threads pitched in thesame direction, one being longitudinally movable, the otherlongitudinally fixed, separate means for driving them in the samedirection the driving means of the movable screw being independent ofthe relative longitudinal position of the screws and the driving meansof the longitudinally fixed screw being adapted to change its speed inresponse to the change in relative longitudinal position of the twoscrews.

20. A speedometer for motor vehicles and the like comprising twoelectric motors, means for driving them, a shaft driven by each motor,said shafts being parallel, said shafts carrying meshing screws, one ofsaid screws being rigidly mounted on its shaft, the other mounted forlongitudinal, motion with relation to its shaft and to the other screwand means for recording speed governed by said longitudinally movingscrews.

21. In a speedometer for motor vehicles and the like a screw threadedshaft and means for rotating it, a track bar parallel thereto, acarriage mounted to travel therealong, a screw controlling the movementof said carriage along the track bar said screw being in mesh with thescrew threaded shaft, means for rotating said screw to move it along theshaft, a speed indicating mechanism and a connection between saidmechanism and the roller carriage.

22. In a speedometer for motor vehicles and the like two parallel shaftsand means for rotating them a screw thread rigidly mounted on one shaft,a screw in mesh with it mounted for longitudinal movement along theother shaft, track bar parallel to said shafts, a carriage mounted totravel therealong, a connection between the carriage and the travelingscrew, speed indicating mechanism and a connection between saidmechanism and the carriage.

In a speedometer for motor vehicles and the like two parallel shafts andmeans for rotating them a screw thread rigidly mounted on one shaft, ascrew in mesh with it mounted for longitudinal movement along the othershaft, track bar parallel to said shafts, a carriage mounted to traveltherealong, a yoke depending from said carriage engaging the ends of thetraveling screw, speed indicatin mechanism and a connection between saidmechanism and the carriage.

24. In a speedometer for motor vehicles and the like a plurality ofelectromagnetic motors, electric circuits therefor, an indicator anddriving connections between it and each motor operating separately on itand means responsive to the position of such indicator for controllingthe speed at which one of said motors is driven comprising means formaking and breaking its electric circuit a plurality of times duringeach revolution to successively excite the electromagnets at intervalsdepending on the position of the indicator.

25. In a speedometer for motor vehicles and the like a plurality ofelectromagnetic motors, electric circuits therefor, an indicator anddriving connections between it and each .motor operating separately onit and means responsive to the 'position of such indicator forcontrolling the speed at whichone of said motors is driven comprisingmeans for making and breaking its electric circuit a plurality of timesduring each revolution to successively excite the electromagnets atintervals varying in length in response to the movement of theindicator.

26. In a speedometer for motor vehicles and the like a plurality ofelectron'lagnetic motors, electric circuits therefor, an indicator anddriving connections between it and each motor operating separately on itand means responsive to the position of such indicator for controllingthe speed at which one of said motors is driven comprising means formaking and breakin its electric circuit a plurality of times during eachrevolution to successively excite the electromagnets at intervalsdepending on the position of the indicator said means consisting of acam shaft parallel with the path of movement of said indicator and meansfor rotating it, a plurality of vanes mounted longitudinally thereon, aroller adapted to contact them successively as the cam shaft is rotated,said vanes tapered uniformly toward one end of the cam shaft, and meansfor making an electric circuit through said (:am shaft and contactingroller to the motor. 27. In a speedometer for motor vehicles and thelike operated by a plurality of electromagnetic motors, electriccircuits therefor means for controlling the speed at which one of saidmotors is driven comprising a circuit making and breakin deviceconsisting of'a cam shaft rotated y said motor, a

plurality of vanes mounted longitudinally thereon, a track rod arallelwith said cam shaft, a frame depencfing therefrom, a roller mounted onsaid frame ada ted to contact said vanes as they rotate, an means forsetting up an electric circuit through said roller and cam shaft to themotor.

28. In a speedometer for motor vehicles and the like operated by aplurality of electromagnetic motors, electric circuits therefor meansfor controlling the speed at which one of said motors is drivencomprising a circuit making and breaking device consisting of a camshaft rotated by said motor, a plurality of vanes mounted longltudinallythereon, a pluralit of track rods parallel with said cam sha t, a dashpot depending from one of said rods, a piston rod extending therefrom, aframework mounted on a second track rod pivoted to said piston rod, aroller mounted on said frame adapted to contact said vanes as theyrotate and means for setting up an electric circuit through said rollerand cam shaft to the motor.

29. In a speedometer for motor vehicles and the like operated by aplurality of electromagnetic motors, electric circults therefor meansfor controlling the speed at which one of said motors is drivencomprising a circuit making and breaking device consisting of a camshaft rotated by said motor, a plurality of vanes mounted longitudmallythereon said vanes uniformly tapered toward one end of the cam shaft, atrack rod' parallel with said ca'm shaft a frame depending therefrom, aroller mounted on said frame adapted to contact said vanes as theyrotate, and means for setting up an electric circuit through said rollerand cam shaft to the motor and means for controlling the intervals ofcontact by moving said roller longitudinally along the cam shaft.

30. In a speedometer for motor vehicles and the like operated by aplurality of electromagnetic motors, electric circuits therefor meansfor controlling the speed at which one of said motors is drivencomprising a circuit making and breaking device consisting of a camshaft rotated by said motor, a plurality of vanes mounted longitudinallythereon said vanes uniformly tapered toward one end of the cam shaft, aplurality of track rods parallel with said cam shaft, a dash potdepending from one of said rods, a piston rod extending therefrom, aframework mounted on a second track rod pivoted tervals of contact bymoving said roller longitudinally along the cam shaft.

31.. In an electric speedometer for motor vehicles and the like, meansfor making and breaking the current comprising a track shaft'and aparallel cam shaft, a cam contacting member movable along the trackshaft, a plurality of vanes mounted longitudinally along the cam shaft,means for passing an electric current through said cam shaft and saidcam contacting member, and means for rotating said cam shaft alternately to make and break the contact of the vanes and the .camcontacting member.

32. In an electric speedometer for motor vehiclesand the like, means formaking and breaking the current comprising a trackshaft and a parallelcam shaft, a cam contacting member movable along the track shaft, aplurality of vanes mounted longitudinally along-the cam shaft, means forpassing an electric current through said cam shaft and said camcontacting member, and means for rotating said cam shaft alternately tomake and break the contact of the vanes and the cam contacting member,said vanes tapered toward one end of the cam shaft.

33. In a speedometer for motor vehicles and the like operated by aplurality of electromagnetic motors, electric circuits therefor,parallel shafts rotated each by a motor, a longitudinally fixed screwmounted on one shaft, a longitudinally movable screw in mesh with it,mounted on the other, a yoke movable with said screw, a track barparallel with the shafts, a cam contacting member mounted thereon, andlongitudinally movable therealong, a positive connection between saidmember and said yoke, a cam shaft parallel with said track bars, andadapted to be rotated by one of said motors, said cam shaft positionedperiodically to contact said cam contacting member.

In testimony whereof, I affix my signature in the presence of twowitnesses this 14th day of March, 1917.

GUY W. BLACKBURN.

Witnesses:

MINNIE M. LINDENAU, MARION L. INGRAHAM.

